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FSX Volumetric Grass Testing

Messages
226
Country
germany
Hey there,

I'm playing around with a technique creating volumetric grass using only 20 planes which means - no impact on FPS.
Its just duplicated planes with a shift of about 0.5cm in z-direction which means the grass is about 10cm high.
The rest is playing around with the alpha channel and playing around with z-bias parameters.

This technique beats everything I've seen before in creating a realistic looking grass field.
BUT:

You can see some flickering when zooming out because the planes are defined as models instead of groundpolygons.

Is there a way of preventing this? I can't define them in general as groundpolygons because MCX sorts them out and I've only one texture on the planes.

And what do you think in general? Does anybody have experience with this, tipps, tricks, improvements?

VolGrass.jpg
 
A

Aviasim

Guest
That looks outstanding to me! where did you find this technique? provide a link please!
 
Messages
226
Country
germany
For better understanding:

In 3dsMax/GMAX it looks like this:

VolGrass4.jpg


20 Layers, same texture + opacity map gives a nice effect and no FPS impact :)

I tested a little more and exported it as a 2002-groundpolygon.
The effect is the same but now the plane-shadow is visible again and the grass itself is a little blurry but thats not bad, it gives the grass a nice touch.
 

arno

Administrator
Staff member
FSDevConf team
Resource contributor
Messages
31,256
Country
netherlands
Hi,

Interesting approach. Did you fix your flickering already?
 
Messages
226
Country
germany
Hey,

I'm glad that you like it!
The flickering problem is solved as soon as the layers are defined as FS2002-style groundpolygons. But then the alpha-channel problem comes up, if I get that solved I have beautiful volumetric grass!
http://www.fsdeveloper.com/forum/showthread.php?t=131389

Another way is to export the layers as a simple model using the FSX SDK and setting the alpha test value around 10.
Looks good too and the flickering goes away and I have no alpha channel problem but the aircrafts shadow lies below the grass which doesn't look that nice.

So a combination of both would be the best! I'm working on it :)
 
Messages
1,198
Country
unitedstates
Howz it look higher up? I would think you would start seeing patterns of repeating tiles. That is by far the best kept lawn I have seen at an airport! :p

nice approach
 
Messages
226
Country
germany
Yeah, you are right, it looks tiled from higher up but the solution for that is to edit the mipmaps alpha channel so the grass nicely smoothes out. (For FS2002 style groundpolygons)

Exporting the grass as a FSX model its playing around with the alpha test value (around 10 should be good).


Its the best kept lawn :) My idea was to add some more polygons and start slicing out pieces. That would give different heights.
And to make the grass look a bit more chaotic I'm thinking of moving the layers only a few millimeters and see what I'll get (-> Illusion of bending...).

Anyways, this is only for the detail junkies. When you're sitting in a virtual cockpit it looks like normal grass (and quite realistic btw!).
The problem is: The more realistic it should become, the more polygons you have to add.

And this 20-layer solution is the best I've found so far to simulate a realistic looking grass area thats as big as you want it to be without FPS-loss!
 

jtanabodee

Resource contributor
Messages
3,912
Country
thailand
Look really nice.
I thought I saw a tutorial once but never try that.
How about moving the plane a bit and give an offset each plane? The grass will move a bit as if there was a wind.

I have to try that.
 
Messages
226
Country
germany
I think what you are suggesting is what I was thinking about, I'll give it a try!
Or are you talking about animating the layers so theres constant movement in it?
Would be hard to realize that but should work too...
 

jtanabodee

Resource contributor
Messages
3,912
Country
thailand
If you can animate that, it would be nice. But I think it cannot export as ground poly, or it can? Please tell us with your progress.
 
Messages
226
Country
germany
Hey there,

I had no time so far to start testing.
The problem would be, like jtanabodee mentioned that it can't be exported as a FS2002 groundpoly anymore, which is so far the most stable variant.
The flickering is gone when exporting as a normal object if you make every mipmap beyound the 32*32px version solid black (assuming your base texture is 1024*1024px large).
That way, animation would work.
But I don't know whether the 3D effect would be still visible because the straight lines consisting of simple green dots that create the effect would be messed up. As far as I know its just the brain connecting the dots to a line in z-direction...
Very interesting topic, I'll do some testing on it and let you know.
 
Messages
226
Country
germany
Hey there,

I did some more research on volumetric grass and encountered
first problems on older systems.
But at first some screenshots on what you can do with it.

What I like the most is that you can attach it nicely to your objects
and areas that should be without grass.
Furthermore it creates an illusion of real grass throughout the whole airfield,
not only the parts where the pilot stays the most like it is with normally designed plants which reduce performance.

I worked a lot on colours and the alpha channel to make it look more realistic.
The first shown screenshots were way too lightly green.

FSD1.jpg


FSD2.jpg


FSD3.jpg

Furthermore I found a solution to prevent tiling effects in farer distances.
I edited the alpha channel in a way that it slowly fades out into black, creates a cool looking effect!

Concerning the problems on some systems, I started this thread without knowing it was caused by the volumetric grass:

http://www.fsdeveloper.com/forum/showthread.php?t=166319

I did some research on the problematic graphics card (7600GT)
and found something interesting:

http://www.passmark.com/forum/showthread.php?t=1989

"There are also very significant differences between XP and Vista. Especially for semi transparent (alpha channel operations)."

That could be it...because the volumetric grass draws 20 alpha channels above each other
which could cause problems on some systems/graphics cards as "hcornea" already guessed in the other thread.

Does anybody know if theres a chance to solve this problem? Maybe some driver setting etc?

Anyways, if you have questions about creating volumetric grass and whatnot, feel free to ask.
One guy already asked me about more details but I'm not having enough time on writing a tutorial.
I could do that someday if more of you also want to add volumetric grass to your airfields/airports.
Let me know.
 

jtanabodee

Resource contributor
Messages
3,912
Country
thailand
Congraturation, Thunderbolt. It looks fantastic
The link that you showed us is the same one that I read about a year ago but I never tried that.
http://www.webdesign.org/3d-graphics/tutorials/low-poly-grass-and-hair.543.html

Would you mind posting your texture and alpha channel? I think I can follow your steps without tutorial.
I think it is possible to make it separate bgl and tell the user if there is a problem you can take this file out.
 
Last edited:
Messages
1,039
Country
belgium
Hi,

Sorry, I am not so smart as jtanabodee... a step-by-step tutorial is needed... :D and I hope "Thunderbolt" can honour his name by writing it and find the time to do it.
It's a very important step forwards in designing and enhancing scenery. He has already accomplished a lot... so felicitations for that !:teacher:

Thanks. José.
 
Messages
226
Country
germany
Thanks for the kind comments, I'm glad that you like it!
I wrote a tutorial in a rush...so if you still have questions you may ask.
The texture is included in the package which you can download here:

Twentynine Palms Scenery Design

The texture is summer only, I didn't create seasonal textures so far.

And now have fun :)

P.S.:
Please don't use the texture in any commercial products. Thanks!
 

jtanabodee

Resource contributor
Messages
3,912
Country
thailand
Bravo Thunderbolt. Thank you for your help.
I did a volume grass in VTSP with my own texture and alpha channel. I did that once but was not good. I know what was my problem the last time. I mapped the texture too big. The texture should be repeated more to make the single grass column closed together.

What I did is make array at 0.01 m in Z axis and make it 15 layers.
I think it depends on which type of airport it is. If you use this from small airstrip it should be like what you do. But VTSP is a big airport, so I try to decrease layer to help fps.

volgrass.jpg


volgrass02.jpg


Not bad at all isn't it.
I think satellite photo underneath will help with the variation in color of the grass.
 
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